Antenna



Jan. 5, 1932. vo ARCO T L 1,839,426

ANTENNA I Filed July 16, 1925 Fig.1 Fig. 2

will:

MINI" INVENTOR I OTAF GEORG. VON ARCO WALTER swarm:

A ORNEY Patented Jan. 5, 1932 UNITED- srx res PATENro FIc GaAn enonevoN ARGO AND WALTER scHAnFnn, or BERLIN, GERMANY, AssIGNons T0 GESELLSCHAFT Fun nnen'rtosn TELEGRAPH-IE M. B. n,

A GORPOBATION OF GERMANY or BERLIN, GERMANY,

ANTENNA Application filed July 16, 1925, Serial No; 43,927, and in Germany July 25, 1924. I

One object of the invention is to provide an antenna which shall have improved reception and radiating characteristics.

Another object of the invention is to provide an antenna coupled to its working circuit by'devi'ces which insert little or no self inducp g other words, merely of a vertically rising tance in the antenna circuit.

Still another object of the invention is to provide an antenna in which the distribution of potential shall be favorable for optimum radiation and reception characteristics.

The invention is illustrated in the accompanying drawings in which the several figures show various applications of the invention.

Fig. 1 shows an arrangement in which the coupling coil L1 connected with the antenna is coupled as closely as feasible with the coil L2 inserted in the exciting circuit, so that practically no stray self-inductance is present.

In Fig. 2 the assumption is made that the stray in the coupling between L1 and L2 was not entirely avoidable, the resultant stray inductance being compensated by the provision of condenser C.

In Fig. 3, C is a capacitive coupling between the exciting circuit and the aerial. In this manner an intentional shortening of the antenna, in a capacitive sense, is produced.

In Fig. 4: is shown an aerial working with a higher harmonic which is coupled with the exciting circuit A at C1 by capacitive means. In the aerial itself, shortening condensers C2, C3, are provided at each potential nodal point, with the end in view of imparting to the antenna by positive means, a distribution of potential having a favorable effect upon the radiation.

A sending aerial is normally excited by coupling it to a generator which produces a wave that is substantially longer than the natural period of the antenna, and the antenna, by the aid of extension means, is tuned to the wave of the generator. Usual practice has been to build aerials consisting of a ver-v tically ascending wire at the upper end of which there is provided a large capacity. These are the usual types such as T-antenna, L-antenna 0r umbrella antenna.

In experiments made on aerials which did not operate with their fundamental period,

but rather on'a higher harmonic, it was discovered that the reception energy was considerably larger, at the same power expenditure. The antenna used in these experiments did not consistof a wire with an end capacity, but of an antenna without such a capacity, in

wire. The cause underlying this good result may be explained in different ways. It is probably that in the case of an antenna excited at a harmonic, the last end of a quarterwave'behave's in a similar way as if an antenna with the'same wave-length were excited at its fundamental period. The measurements made-of the antenna resistance in both cases gave the same results, whence the inference may bedrawn that the radiation resistance in both instances was the same. This will also appear plausible and apparent because the configuration of the potential distribution is larger may reside in that:

1. The part doing sub-stantially'most of the radiation work, that is, the upper end of the antenna is farther removed from the ground corresponding to a quarter wave-length compared with the arrangementthat has formerly been used, and in that losses are causedto a considerably less extent;

' 2 The configuration of the potential distribution with an antenna end which oscillates at its own natural-period without extension meansbeingused, results in a radiation giving much more favorable conditions.

The potential distribution curve at the antenna, furthermore, may under certain cir-' cumstances be dependent, upon the wavelength used, and it may be possible that apart from what hasbeen stated above, the radiation conditions for waves falling below can tain lengths may be more favorable than for longer waves. 3 Still, this possibility leaves the .ideaunderlyingthe present invention quite unaffected. I

"If'it is correct that the configuration of the potential curve of the radiating antenna end is the cause underlying the good result obtained, it is, immaterial whether an antenna is used that operates or is excited with its harmonic or its fundamental wave. The only condition is that the antenna should .not be lengthened by special means. On the other hand, it may even be possible-that by the shortening of the antenna the conditions for radiation maybecome even more favorable than in the case of the straight wire.

Now, the present invention consists in that in the antennae, regardless of whether they oscillate at their fundamental wave or at a higher harmonic, the conditions are so chosen that the most favorable or optimum conditions for radiation are obtained. The means adopted for this purpose are the.following:

If an antenna is concerned which oscillates at its fundamental period, care must be taken that its coupling with the generator is made Without a self-inductance having a lengthening action upon the antenna. This I can be accomplished as shown in Fig. 1, by

placing the coupling inductance, which must consist of but a few turns, in extremelyclose space. coupling relation with the coupler coil of the generator, in order that stray inductance may be avoided. If it should not be feasible to prevent the arising of stray inspatial relation to substantially eliminate stray inductance.

2. An antenna system comprising an antenna, a circuit coupled to said antenna and means for coupling said circuit to said antenna comprising a coil of a few number of turns in said antenna without materially a1- tering the electrical length thereof and a coil in said circuit in close spatial relation- -.ship and a condenser associated with said coils for neutralizing the tendency of the inductive coupling to lengthen the natural Wave length of the. antenna.

3. An antenna system comprising an antenna, an energizing system coupled thereto, and means for coupling said energizing circuit to said antenna without altering the electrical length thereof, comprising a coil of a few number of turns in said antenna closely coupled to a coilhaving airelatively great number of turns in said energizing cir-- cuit.

GRAF GEQRG VON ARGO. WALTER SCHAFFER.

ductance in such measure as may be desired,

this can be neutralized'by the provision of a condenser as shown in Fig. 2, and may, if necessary, be soadjusted that there'is an excess of capacitance. This plan is particular- ,ly suitable because, under certain circumstances, such excess of capacitance may result in potential configuration that is especially favorable. The same end maybe attained if, in lieu ofinductive'antenna coupling, capacitive coupling is resorted to. This isillustrated schemetrically inFig. 3. WVhat has been pointed out above holds good for antennae which operate at their natural period. In the case of aerials'which are worked at one of their harmonics, the configuration of the potential curve is most natural and most satisfactory a priori at every potential node especially the last one,

seeing that at these latter points there are no distorting extension means.

Under certain circumstances, the situation may be 

